Tomato mosaic virus (ToMV) with Potato virus x (PVX)
Symptoms occur on young leaves as small, brown spots and on petioles and stems as narrow, dark brown streaks. Lesions may coalesce to form large, dead areas and leaves curl downward. Lesions on the fruit are small and only skin deep, but may run together, forming large lesions. These lesions give a greasy appearance to the fruit, which eventually may become rough and misshapen.
Conditions for Disease Development
Individually, ToMV and PVX are easily transmitted mechanically by greenhouse workers, their tools and on cultivation equipment. However; for this disease to occur, both viruses must be present in the same plant. If young plants already infected with ToMV become infected with PVX, double streak occurs. Severity of symptoms are affected by virus strains. plant age and day length.
The use of ToMV-resistant varieties in combination with the cultural practices of roguing infected plants and avoiding handling of potatoes prior to working with tomatoes will reduce losses from this disease. Also, not planting in fields that were planted to potatoes the previous season and sterilizing workers’ tools after handling infected plants can help reduce disease incidence.